Long Term Evolution (LTE) is an improved universal mobile telecommunication system (UMTS) that provides higher data rate, lower latency and improved system capacity. In LTE systems, an evolved universal terrestrial radio access network includes a plurality of base stations, referred as evolved Node-Bs (eNBs), communicating with a plurality of mobile stations, referred as user equipment (UE). A UE may communicate with a base station or an eNB via the downlink and uplink. The downlink (DL) refers to the communication from the base station to the UE. The uplink (UL) refers to the communication from the UE to the base station. LTE is commonly marketed as 4G LTE, and the LTE standard is developed by 3GPP.
Starting from April 2013, 3GPP started a new study item (SI), “Network Assisted Interference Cancellation and Suppression” (NAICS), to investigate the benefit on system throughput by leveraging receiver's capability of interference cancellation. Various types of interference cancellation (IC) receivers are shown to provide significant gain if some characteristics of interference are available at victim nodes. Commonly investigated IC techniques in literature may include symbol-level based IC (SLIC) and codeword-level IC (CWIC). SLIC is an IC technique that detects interfering signal, which is supposed to be finite-constellation modulated, in a per-symbol basis. CWIC is referred to that a receiver decodes and re-encodes interference codeword to reconstruct the contribution of the interference signal on its received signal. Comparing to SLIC, a receiver needs more information on interference to access CWIC, such as modulation and coding scheme (MCS) index and the rule scrambling the bit stream of interference. Obtaining the interference characteristics, such as the modulation order or encoding rules of the interfering signal, is important for IC techniques. The characteristics could be either blindly detected by victim receiver or informed from network side.
In the NAICS study item, various parameter candidates helpful for interference cancellation were identified. For example, parameters that are higher-layer configured per the current specifications (e.g., transmission mode, cell ID, MBSFN subframes, CRS antenna ports, PA, PB); parameters that are dynamically signaled per the current specifications (e.g., CFI, PMI, RI, MCS, resource allocation, DMRS ports, nIDDMRS used in TM10); and other deployment related parameters (e.g., synchronization, CP, subframe/slot alignment). Although it is possible to let receiver detect or estimate these parameters associated with the interfering signal without any aid of signaling, the complexity cost could be very huge to estimate them. The current LTE system provides sufficient signaling and reference signals supporting the channel estimation only for desired-signal link, but not for interference link. Solutions to obtain the characteristics of interference or enhance the reliability to estimate these parameters are sought.